Republican policies on illegal immigration are annoying Latinos and becoming a serious handicap in the presidential election

IT MAY have taken the Supreme Court just an hour to wrap up its discussion of illegal immigration this week, but America's politicians, it seems, cannot get enough of the subject. It will be several months before the court rules on the case in question, which concerns a state law in Arizona, but Democratic leaders in the Senate are already planning a vote to overturn its decision if the law is upheld. That vote would presumably fail, thanks to Republican opposition, but it would allow the Democrats to keep the subject in the news. Democrats are also attacking Mitt Romney, the presumptive Republican nominee for president, for supporting the law. Mr Romney, meanwhile, has dismissed the whole fuss as an effort to distract Hispanic voters from Mr Obama's failings as steward of the economy. The outcome of the presidential race, both sides acknowledge, could conceivably hinge on whether it is the state of the economy or laws like Arizona's that stir more indignation among Hispanics.

Arizona's bill, passed in 2010, seeks to discourage illegal immigration by making it a crime under state as well as federal law and by instructing state authorities to be on the lookout for illegal immigrants. Civil-liberties groups worry that this will lead to harassment of anyone with brown skin, even though the law expressly prohibits such “profiling”. There is no easy way for the authorities to judge an individual's immigration status, argue opponents, so many citizens will be subjected to unwarranted checks.

That prospect seemed to concern several justices during the oral arguments on the law before the Supreme Court. Stephen Breyer, for example, fretted about the possible fate under the law of a jogger carrying only a driver's licence from New Mexico, a state that borders Arizona and used to issue licences to illegal immigrants. But the solicitor-general said he was not challenging the law on the grounds that it would discriminate against Latinos. Instead he argued that the law pre-empts the federal government's power to set immigration policy. Its defenders retort that it aims only to help the federal government fulfil its obligations on immigration, and that only an administration that was deliberately neglecting them could find fault with it.

The Supreme Court's verdict will determine the fate not just of Arizona's law, but of similar measures in five other states. As successive presidents have promised but failed to tackle the question of America's 10m-odd illegal immigrants, frustration at the federal government's inertia has grown, especially among conservative voters. Republican-controlled legislatures in several states have attempted to take matters into their own hands. The need for a crackdown on illegal immigration seems to have become an article of faith among Republican primary voters. The presidential bid of Rick Perry, the governor of Texas, came to grief partly because he had signed a law allowing certain undocumented students to pay the same rates as other state residents at public universities.

Even as the debate about illegal immigration has become shriller, the phenomenon itself has declined. The recession has helped to stem the flow of job-seekers across America's southern border. Despite more vigorous policing, the number of people caught trying to cross has declined markedly. This week the Pew Hispanic Centre, a research institute, released a report arguing that Mexicans, who once accounted for most of the illegal influx, are now leaving the country in greater numbers than they are entering it.

Nonetheless Mr Romney cheerfully joined in the denunciation of Mr Perry for his breach of party doctrine. By the same token, when Newt Gingrich, another candidate for the Republican presidential nomination, suggested that illegal immigrants of good character and long standing should be allowed to stay, Mr Romney attacked him too. He argues that life should be made so difficult for illegal immigrants that they will choose, in a horrible phrase, to “self-deport”. Democrats hope that all this will dent Mr Romney's prospects among Hispanic voters, many of whom see Republican fulminations against illegal immigration as stony-hearted, if not racist. In a survey conducted last year on behalf of the Pew Hispanic Centre, two-thirds of Hispanic registered voters said they favoured the Democrats. Just 20% identified themselves as Republican. In March a Fox News Latino poll found that, in a head-to-head match-up, Mr Romney would carry just 14% of the Hispanic vote. Earlier polls had found Mr Romney doing better than that, but still considerably worse than the 31% John McCain managed to amass, even while losing in 2008, or the whopping 40% George W. Bush posted in 2004.

Hispanics made up 16% of the population in 2010, according to that year's census. They are a fast-growing group, although a relatively large proportion of them are below voting age and even those eligible to vote are less assiduous about it than Anglos are. But they account for over 20% of the population in several swing states, including Colorado, Florida, Nevada and New Mexico. Democrats hope to make Arizona a swing state this year, thanks both to the 30% Hispanic share of the local population and to the acrimony inspired by the state's immigration law. A recent poll put Mr Obama within two points of Mr Romney in the state, which has been a Republican stronghold recently—not least because of Mr McCain's candidacy in 2008.

The Romney campaign argues that immigration is not the only point of contention for Hispanic voters. Latinos suffer higher unemployment than the national average, and are more likely to be poor. Their incomes are still lower, on average, than when Mr Obama came into office. Even for Mexican-Americans, who make up nearly two-thirds of America's Hispanic population and seem particularly suspicious of Mr Romney, immigration reform may matter less than jobs or schools.

Republicans have long tried to find common cause with Latino voters. They point out that, in some respects, Hispanics seem natural conservatives: religious, hard-working and with close family ties. There is even talk that Mr Romney might bolster his standing among Latinos by picking one as a running-mate—Marco Rubio, a senator from Florida, say, or Susana Martinez, the governor of New Mexico.

Since the immigration debate has such a nativist tone, however, Democrats are doubtful that Republicans can win over many Hispanic voters. “You can't do it when at a very baseline level you make American citizens feel unwelcome in their own country,” says Joaquin Castro, a Democratic state representative from San Antonio, Texas. It will not help that in the middle of the campaign the Supreme Court will draw attention once again to the Republicans' obstreperousness on the issue by ruling on the Arizona law.